The present invention relates to drip irrigation hoses, and to methods of making such hoses.
Drip irrigation hoses are increasingly being used for irrigating various types of plants since they supply the water directly to the root regions of the plants, and therefore are highly conservative of water resources. One type of irrigation hose is constructed by extruding a plastic hose and simultaneously bonding to its inner surface a plurality of emitter elements, or a strip of emitters, spaced longitudinally of the hose for discharging the water at a slow rate via discharge openings formed in the hose. Another type includes a sheet of flexible plastic material formed into a seamed hose, with the emitter elements bonded within the seam or to another part of the hose for discharging the water at a slow rate through discharge openings in the hose. The present invention is applicable to both types of drip irrigation hoses.
Examples of drip irrigation hoses of both types are described in U.S. Pat. Nos. 4,196,853; 5,163,622; 5,183,208; 5,203,503; 5,246,171; 5,333,793; 5,522,551; 5,620,143; 5,695,127; and 5,785,785.
One problem in using drip irrigation hoses is the difficulty in ensuring relatively uniform discharge rates along the length of the hose. This problem is particularly acute where extremely long lengths of the hose are used since the hose itself produces a pressure drop along its length tending to decrease the discharge rate of the emitters at the end of the hose. This sensitivity of the discharge rate to the water pressure is also a problem where the land being irrigated is not flat and even.
Another problem with such drip irrigation hoses is sensitivity to clogging, and the difficulty in dislodging clogging particles.
In addition, such drip irrigation hoses are frequently used for only a single season, or for relatively few seasons. Accordingly, the cost involved in producing such drip irrigation hose is a significant factor in their use.
An object of the present invention is to provide a drip irrigation hose in which the discharge rate from each emitter element is less sensitive to changes in the pressure of the water within the hose at the respective emitter element. Another object of the invention is provide a drip irrigation hose which has less sensitivity to clogging, and which more conveniently permits clogging particles to be dislodged. A further object of the invention is to provide a drip irrigation hose of a construction which can be produced in volume and at relatively low cost. A still further object of the invention is to provide a method of making such drip irrigation hoses.
According to one aspect of the present invention, there is provided a drip irrigation hose, comprising: a hose for conducting pressurized water through its interior and formed with a plurality of outlets for discharging the water at longitudinally-spaced locations along the length of the hose; and a plurality of emitter elements secured to the hose at longitudinally-spaced locations along its length to define a plurality of turbulent flow passageways each communicating with the interior of the hose for discharging water from a hose outlet at a slow rate; characterized in that the turbulent flow passageways are defined by a relatively elastic material coextruded with a relatively stiff material such that the relatively elastic material is pressure-deformable as compared to the relatively stiff material to change the turbulent flow passageways in response to the pressure of the water at the respective emitter element, to thereby provide pressure-compensation of the water discharge rate from the respective outlet.
According to one group of preferred embodiments of the invention described below, the hose is made by overlapping opposed longitudinal portions of thin, flexible sheet material, and welding them together with the coextruded relatively elastic material and the relatively stiff material in-between to define a seamed hose incorporating the two materials in the seam.
According to further features in some of the described embodiments, the welded overlapping portions of the seam further include a plurality of teeth defining the turbulent flow passageway, and a rib laterally of the teeth, the rib being of the relatively stiff material, and the teeth being deformable and made of the relatively elastic material.
In one such described preferred embodiment, the rib is of approximately the same height as the teeth when non-deformed, and the overlying portion of the hose is formed with a slack between the rib and the teeth to permit the pressurized water to apply a tangential force to the overlapping portions of the seam, and thereby to change the shape of the turbulent flow passageways defined by the teeth.
In another described preferred embodiment, the rib is of less height than the teeth when non-deformed thereby permitting the pressurized water to apply a tangential force to the overlapping portions of the seam and to change the shape of the turbulent flow passageways defined by the teeth.
Further embodiments are described below wherein the welded overlapping portions of the seam include a plurality of teeth made of the relatively stiff material, and a strip of the relatively elastic material underlying the teeth.
In one of the latter embodiments, the welded overlapping portions of the seam include a plurality of teeth constituted of an inner layer of the relatively elastic material, and an outer layer of the relatively stiff material. In another described embodiment, the welded overlapping portions of the seam include a plurality of teeth made of the relatively stiff material with at least the outer portions of the teeth made the relatively elastic material.
A further embodiment is described, wherein the overlapping portions, of the seam include a plurality of teeth having one side made of the relatively stiff material, and the other side made of the relatively elastic material. Preferably, in the latter embodiment, the side of the teeth made of the relatively elastic material and is of greater height than the side made of the relatively stiff material.
According to another group of embodiments described below, the hose is a continuous unseamed hose, and the plurality of emitter elements include a plurality of teeth carried by a base strip welded to the inner surface of the hose and defining the turbulent flow passageways.
According to further features in some of these described embodiments, the base strip also includes a rib of a relatively stiff material welded between the base strip and the inner surface of the hose. In one described embodiment, the rib is of approximately the same height as the teeth, and the hose is formed with a slack between the rib and the teeth to permit the pressurized water to apply a tangential force to the teeth and thereby to change the shape of the turbulent flow passageways. In another described embodiment, the rib is of less height than the teeth such as to permit the pressurized water to apply a tangential force to the teeth and thereby to change the shape of the turbulent flow passageways.
According to another aspect of the invention, there is provided a drip irrigation hose, comprising: a hose for conducting pressurizing water therethrough and formed with a plurality of longitudinally spaced outlets for discharging water therefrom; and a plurality of emitter elements at least partly made of relatively elastic material welded at longitudinally-spaced locations along the inner surface of the hose and defining a plurality of restricted flow passageways to the plurality of hose outlets for discharging water from each outlet at a slow discharge rate; the hose carrying a longitudinally-extending rib of relatively stiff material welded between the emitter elements and the inner surface of the hose such that when the water within the hose is pressurized, the pressurized water initially tautens the hose and changes the shape of the restricted flow passageways, to thereafter decrease the sensitivity of the water discharge rate from each outlet to changes in pressure of the water within the hose.
According to a further aspect of the invention, there is provided a method of making a drip irrigation hose, comprising: coextruding a strip of a relatively stiff material and a strip of a relatively elastic material on a substrate; forming at least one of the strips into a plurality of emitter elements at longitudinally-space locations along the length of the substrate; and utilizing the substrate including bonding the coextruded strips thereon to produce a hose having the plurality of emitter elements welded thereto to define a plurality of turbulent flow passageways to discharge openings in the hose for discharging water from the hose at a slow rate.
In some described embodiments, the substrate on which the strips are coextruded is one edge of a flexible sheet which edge is overlapped with and bonded to an opposite edge of the flexible sheet to produce a seamed hose with the emitter elements welded within the seam. In other described embodiments, the substrate on which the strips are coextruded is welded to the inner face of a seamless hose.
As will be described more particularly below, a drip irrigation hose constructed in accordance with the foregoing features provides pressure compensation in the discharge rate from each emitter element, thereby making the discharge from each emitter element less sensitive to changes in the pressure of the water within the hose at the respective emitter element. In addition, such drip irrigation hoses have a relatively low sensitivity to clogging. In addition, and as will be described more particularly below, certain embodiments of the invention produce not only compressional forces, in the emitter elements, but also tangential forces which tend to dislodge clogging particles. Further, and as will also be more particularly described below, such drip irrigation hoses may be made in volume and at relatively low cost.
According to a further feature of the invention, the relatively elastic material can be extruded intermittently for each emitter, rather than continuously for the complete strip, thereby significantly reducing the cost of making the drip irrigation hose.
Further features and advantages of the invention will be apparent from the description below.